A method is known in which a radiation image used for medical diagnosis is converted into digital data, the data are image-processed utilizing a computer so as to be more suitable for diagnosis, and the image is reproduced by exposure to laser beams.
For the laser beams, lasers such as semiconductor lasers or helium-cadmium layers are commonly used as light sources of such a scanner-type recording apparatus.
Of these, the semiconductor lasers have many advantages such that they are compact in size and inexpensive, and yet can be readily modulated and have a long lifetime.
On the other hand, it is necessary for light-sensitive silver halide photographic materials adapted thereto, used for laser scanners, (hereinafter "light-sensitive materials for laser scanners") to be spectrally sensitized to regions of from the red region to the infrared region, having wavelengths of 600 nm or more, and cyanine dyes are commonly used.
In recent years, achievement of rapid processing of light-sensitive materials has made great strides, and the light-sensitive materials for laser scanners are also no exception thereto. That is to say, there is a strong demanded for making the development processing time shorter for the reason that it is desired to catch image information more rapidly.
Achievement of rapid processing of such light-sensitive materials, however, is not necessarily so simple as in the case of other light-sensitive silver halide photographic materials, because such light-sensitive materials for laser scanners have difficulties peculiar to themselves. Namely, development non-uniformity tends to be caused in the resulting image after development. This is presumably because a latent image formed as a result of exposure to a high-intensity light for a short time using the laser beams tends to be influenced by the changes in development conditions such as processing time, processing temperature, and stirring. In particular, the development temperature dependence is remarkable.
In relation to methods of preventing such development non-uniformity, a method in which a specific surface active agent is used is known, which is an attempt as disclosed, for example, in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 29835/1989 or No. 148257/1988.
However, as the development processing is made more rapid, such conventional techniques can not be said to be satisfactory. For example, when the development time is within several ten seconds, a photosensitive layer in a developing solution may become very susceptible to the diffusion phenomenon that the concentration of a developing solution in a film shifts from a low-density image region to a high-density image region and finally becomes uniform over the whole region. In particular, the development temperature has a great influence in view of the fact that it governs the degree of swell of a film.
As another problem, from the view point of photographic performance, the above techniques have been involved in the problem that the maximum density can be obtained with difficulty, the resulting silver image has a yellowish tone as a result, and a tone of neutral gray, which is advantageous for the evaluation of an image, can not be obtained.